Several types of timing signals have to be derived from the incoming digital video signal by the input interface of a digital video recorder. These timing signals need to be produced by so called flywheel circuits even if the input signal disappears or is not continuous, or even if the signal is severely distorted. The phasing has to be immune to disturbances that may come with the input video data. In prior art systems, the flywheel phasing (forced loading of the flywheel counters with constant numbers by the sync components extracted from the incoming data) is enabled as long as the input data is present and free of disturbance. It is disabled as soon as a disturbance is detected. However, this method creates a problem, and that is that the process of detecting the disturbance and making the decision to disable the phasing takes time. During that time the phasing of the flywheel circuits can be disturbed.
The flywheel circuits have to be initially phased to the synchronization components of the input video signal and rephased every time a change is detected in the phase relationship between flywheeled signals and the input video signal. Before the phasing of the flywheel circuits is enabled, it must be determined that the video signal is present and stable.
In accordance with an aspect of the present invention there is provided a system and method of detecting the stability of the incoming digital video signal as part of the phasing of the flywheel circuits of the digital component video input interface.